Engine mounts

[Dave-M]

While answering the previous post I thought it might be a good time to ask your opinions on a little project I have on the go:-
After suffering my third engine mount failure in 12 months, and, before you say anything, No it's not my driving, I have started to re hash my old knackered engine mounts with polyurethane in the hope of a little longer life than the current crappy rubber ones.
My question is, has anyone been there and done this?
I don't want to waste my time making moulds and jigs if there is a pre existing solution.
As my car is used daily I suppose it gets more use than most but the failure rate is not very good.
Any help / advice greatly appreciated
Regards
Dave

[stuartgb100]

Dave,

You might like to talk to TTR.

I'm using their uprated/ road engine mounts, as opposed to race mounts.
Seem fine so far.

Might be a place to start?

Regards,
Stuart.

[Dave-M]

Stuart, How long have you had them installed, are they polyurethane, are they the same design as the originals, do they increase the harshness of the engine into the car? Too many questions I know, but your experience with the mounts would be appreciated.
Regards
Dave

[1964 S1]

Hello Dave, in many many Lotus years my personal experience with stock motor mounts has been nearly trouble free. Are you being pursued by the MotorMountWitch? I drive my +2 and S1 with verve, even drag raced them on occasion, and autocross. I had one failure, and it was a slow tear.
However, they are not daily drivers, could this be the difference somehow? My current mounts are at least 8 and 12 years old, but only about 15,000 miles total. In my old old Lotus days, when the cars were only about that old, I never had a failure.
There are other threads here as you probably know concerning this. Did you install them?
I bought crates of parts some years ago and there were several NOS mounts in there, I saved them but as I've never needed one (knock wood) I'll sell you one cheap and you can do market research as to whether or not the new replacement ones are the problem. Eric

[inxs]

Hi Dave,
had an interesting email from Steve at the Elan Factory (Australia) I have just purchased some suspension bits and pieces and a set of engine mounts. Mine are relativley new but are old as the car I purchased was a 16 year rebuild with little use!!

Any way Steve mentioned that they have found that the left mount under the exhaust suffers three to four times the failure rate, this is due to the extractors that most people use and the heat that this mount is subjected too.

I purchased from him a heat shield that goes on this mount for $20.00 AUD, I should get this some time next week, I will post a few pics of this. This may be worth considering.

Cheers Darren

[steveww]

The current quality of engine mounts is totally cr@p

I replaced the original and some what ancient mount on my S4 recently. I purchased the mounts from PM and both failed in about 200 miles as the rubber came "unstuck" from the U shapped bit. I went through 2 sets from PM then got the third set from Sue Miller. I am sure they get their kit from the same supplier and it is just batch quality.

The TTR ones (the non motor sport ones) are modified standard mounts. The gap between the rubber and the U shapped steel bit is filled with silicone (RTV), the similar to the stuff you put around the bath. This makes them slightly stiffer and takes some load off the original rubber. This is still a bit of a bodge though

The TTR motor sport ones are poly and super stiff, no good for road use.

There is certainly room for a good quality fast road type engine mount. Using poly is probably a good idea as I think the quality of rubber is limited these days due to constraints on what goes in to the mix, same as rotoflexes.

Keep us posted with your progress

[Dave-M]

Sorry double post
Dave

[Dave-M]

Right, I'll crack on and will keep you posted.
One thing regarding my failures is that 2 were exhaust side and one carb side so it may be worth looking at the heat shield .
Thanks for all the input
Regards
Dave

[Tonyw]

In my experiance polyurethane comes in different grades it can be soft or hard so it would make a good replacement for rubber, wondering if the torque is stressing the mounts causing premature failure, this may cause the rubber to split but through the rubber and not on the mating surface as long as the bonding from rubber to steel was good though, if it was not good then the bonding would be the weakest point. My thought for what they are worth.

Tony W

[Dave-M]

Tony. It's the metal / rubber interface that's failing. Probably poor quaility rubber (as stated above) and poor quailty control.
It's not through abuse either. I have owned a twin cam powered Lotus of one description or another for the past 30+ years and have not had this problem previously, so I am inclined to agree with Steveww.
Regards
Dave

[ppnelan]

It may be a good idea to check there is no underlying cause for such failures first. Some things spring to mind:

Unbalanced engine components causing excessive vibrations
Badly set-up carbs causing the same
Engine/gearbox assembly misalignment trying to tear mounts apart
Incorrect engine mount-to-block spacers fitted causing the same
Probably many more....

Matthew

[stuartgb100]

Dave,

Can't help much I'm afraid, but I replaced them as part of an anti-vibration campaign.

When removed, I found both rubbers (to a lesser or greater degree), had debonded from the metal.

I knew of this problem and talked to TTR - they said their uprated road version was a significant improvement, so I went that route.

I have only done about 4k miles since (approx 1 year), so no proof yet, but I do not notice much if any difference in terms of harshness.

Can only say that I've had no bad advice from TTR so far.
Fingers crossed.

Regards,
Stuart.

[Dave-M]

Matthew,
There are no issues with balance of either the engine or carbs, The mounts line up just as they should and the spacers are the same as they have been for the last 5 years, 4 of which have been trouble free.

Anyway I have decided to progress my project which I think will be worthwhile as I have come up with a simple progressive engine mount, ie soft and compliant at low loads and progressivley stiffening up the higher the load is.
Keep you posted
Regards
Dave

[poiuyt]

I had a left mount fail when the rubber separated from the metal and the engine dropped the 1/2 inch or so till the metal bottomed out.

I replaced the mount with one from JAE in California which has more rubber that completely fills the U. This can't fail the same way and there have been no problems since (maybe 7000 miles).

Steve B

[steveww]

No problems with alignment or vibration here. I have not changed anything since installing the third new engine mount and that has now lasted 3500 miles and still going strong.

There are just some poor quality parts around. I like the idea of the completely filled mounts from JAE, might consider importing some of those.